How to find out whether guassian or salt& pepper noise present in an image, Is there any algorithm

Question

Is there any algorithm for identifying the noise in an image I have to identify whether the noise present in a mammogram image is guassian or salt& pepper.

Answer 1

Exploit the fact that salt&pepper noise has only 2 values and median filter does excellent job in getting rid of it.

• Filter your image with median filter
• Find pixels where median filter did most of its job
• Plot histogram of those pixels

• Compute fraction of 0s and 1s

  threshold = 0.2; % adjust to perform best on your images
  im = imread('../lena.bmp');
  imd = double(im);
  imd = imd./max(max(imd));
  imdg = imnoise(imd,'gaussian');
  imdsp = imnoise(imd,'salt & pepper');
  subplot(2,2,1), imshow(imdg)
  subplot(2,2,2), imshow(imdsp)
  imdgf = medfilt2(imdg);
  imdspf = medfilt2(imdsp);
  g = imdg.-imdgf;
  sp = imdsp.-imdspf;
  gm = abs(g)>threshold;
  spm = abs(sp)>threshold;
  subplot(2,2,3), hist(imdg(gm))
  subplot(2,2,4), hist(imdsp(spm))
  waitforbuttonpress